Since the discovery of ferrocene in 1951, a number of metallocenes have been prepared by the combination of compounds having cyclopentadiene structure with various transition metals. The term "cyclopentadiene structure" as used herein refers to the following structure. ##STR1##
The term "cyclopentadiene-type compounds" as used herein refers to compounds containing the cyclopentadiene structure. Examples include unsubstituted cyclopentadiene, unsubstituted indene, unsubstituted fluorene, tetrahydroindene, and substituted varieties of such compounds.
Many of the cyclopentadienyl-type metallocenes have been found useful in catalyst systems for the polymerization of olefins. It has been noted in the art that variations in the chemical structure of such cyclopentadienyl-type metallocenes can have significant effects upon the suitability of the metallocenes as a polymerization catalyst. For example, the size and substitutions on cyclopentadienyl-type ligands has been found to affect the activity of the catalyst, the stereoselectivity of the catalyst, the stability of the catalyst, and other properties of the resulting polymer; however, the effects of various substituents is still largely an empirical matter, that is, experiments must be conducted in order to determine just what affect a particular variation will have upon a particular type of cyclopentadienyl-type metallocene. Some examples of some cyclopentadienyl-type metallocenes are disclosed in U.S. Pat. Nos. 4,530,914; 4,808,561; and 4,892,851, the disclosures of which are incorporated herein by reference.
Metallocenes in which two of the metal bound cyclopentadienyl type groups are connected by a bridging structure are referred to bridged metallocenes. Metallocenes in which the metal bound cyclopentadienyl type groups are not connected by bridging structure are referred to as unbridged metallocenes.
While there are references in the prior art which have envisioned metallocenes containing fluorenyl groups, only a very limited number of fluorenyl-containing metallocenes have actually been prepared prior to the present invention. The Journal of Organometallic Chemistry, Vol. 113, pages 331-339 (1976), the disclosure of which is incorporated herein by reference, discloses preparing bis-fluorenyl zirconium dichloride and bis-fluorenyl zirconium dimethyl. U.S. Pat. No. 4,892,851 and the New Journal of Chemistry, Vol. 14, pages 499-503, dated 1990, the disclosures of which are incorporated herein by reference, each disclose preparing a metallocene from the ligand 1,1-dimethylmethylene-1-(fluorenyl)-1-(cyclopentadienyl). The New Journal of Chemistry article also discloses preparing a similar compound in which the cyclopentadienyl radical has a methyl substituent in the number 3 position. The term "fluorenyl" as used herein refers to 9-fluorenyl unless indicated otherwise.
An object of the present invention is to provide new fluorenyl-containing compounds and metallocenes.
Another object is to provide a process for the polymerization of olefins using such metallocenes.